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Electrical services

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the presentation about general information for electrical services like differences between ac and dc current differences between wires and cable types of wiring and fuses

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Electrical services

  1. 1. ELECTRICAL SERVICES Ar. Abhinav Srivastav Assistant Professor B.Arch., M.Tech (IIT-R) Presented By-
  2. 2. OUTLINE- • What is Electricity? • Sources of Electricity • Difference between AC & DC • Conductor o Properties of a good conductor o Classification of conductor o Semi-conductor • Difference between wire and cable o Parts of a cable o Type of cable o Wires o Types of wires • System of wiring o Cleat wiring system o Wooden casing caping wiring system o Lead sheathed wiring system o C.T.S/T.R.S wiring system o Conduit wiring system • Fuses • References Electrical Services
  3. 3. • Electricity is briefly defined as the flow of electric charge • Electricity is all around us–powering technology like our cell phones, computers, lights, soldering irons, and air conditioners. It’s tough to escape it in our modern world. What is Electricity? Electrical Services A very simple atom model. It’s not to scale but helpful for understanding how an atom is built. A core nucleus of protons and neutrons is surrounded by orbiting electrons As our understanding of atoms has evolved, so too has our method for modeling them. The Bohr model is a very useful atom model as we explore electricity A lithium atom (3 protons) model with the charges labeled This is a copper atom diagram: 29 protons in the nucleus, surrounded by bands of circling electrons. Electrons closer to the nucleus are hard to remove while the valence (outer ring) electron requires relatively little energy to be ejected from the atom.
  4. 4. Electrical Services What is Electricity? Terms related to Electricity • Current is the amount of electric charge that flows. When 1 coulomb of electricity moves past somewhere in 1 second, the current is 1 ampere. To measure current at one point, we use an ammeter. • Voltage, also called "potential difference", is the "push" behind the current. It is the amount of work per electric charge that an electric source can do. When 1 coulomb of electricity has 1 joule of energy, it will have 1 volt of electric potential. To measure voltage between two points, we use a voltmeter • Resistance is the ability of a substance to "slow" the flow of the current, that is, to reduce the rate at which the charge flows through the substance. If an electric voltage of 1 volt maintains a current of 1 ampere through a wire, the resistance of the wire is 1 ohm - this is called Ohm's law. When the flow of current is opposed, energy gets used or gets converted to other forms (such as light, heat, or sound)
  5. 5. Electrical Services • Electric energy is the ability to do work by means of electric devices. Electric energy is a "conserved" property, meaning that it behaves like a substance and can be moved from place to place. Electric energy is measured in joules or kilowatt-hours (kWh) • Electric power is the rate at which electric energy is being used, stored, or transferred. Flow of electrical energy along power lines are measured in watts. If the electric energy is being converted to another form of energy, it is measured in watts. If some of it is converted and some of it is stored, it is measured in volt-amperes, or if it is stored (as in electric or magnetic fields), it is measured in volt-ampere reactive • Q is electric charge in coulombs • t is time in seconds • I is electric current in amperes • V is electric potential or voltage in volts What is Electricity?
  6. 6. Sources of Electricity Electrical Services • Thermal Power Plant India's electricity sector consumes about 72% of the coal produced in the country. • Renewable energy India's renewable energy sector is amongst the world's most active players in renewable energy utilization, especially solar and wind electricity generation. • Hydro power The hydro-electric power plants at Darjeeling and Shivanasamudram were established in 1898 and 1902 respectively and were among the first in Asia. • Wind power India has the fifth largest installed wind power capacity in the world. In the year 2015-16, wind power accounted for 8.5% of India's total installed power capacity, and 2.5% of the country's power output. • Geothermal energy • Tidal power • Nuclear power
  7. 7. Difference between AC & DC Electrical Services Alternating Current (AC) Alternating current is defined as the flow of charge that changes direction periodically. The result obtained will be, the voltage level also reverses along with the current. Basically AC is used to deliver power to industries, houses, office buildings, etc AC Source Difference between AC & DC Direct Current (DC) Direct current (DC) is the movement of electric charge carriers, i.e. electrons in a unidirectional flow. In DC the intensity of the current will vary along with time, but the direction of movement stays the same in all time. Here DC is referred to voltage whose polarity never reverses. In a DC circuit, electrons emerge from the minus or negative pole and move towards the plus or positive pole. Some of the physicists define DC as, it travels from plus to minus. DC Source
  8. 8. Difference between AC & DC Electrical Services S No Alternating Current Direct Current 1 The amount of energy that can be carried It is safe to transfer over longer city distances and will provide more power. Practically the voltage of DC cannot travel very far until it begins to lose energy. 2 The cause of the direction of flow of electrons It is denoted rotating magnet along the wire. It is denoted steady magnetism along the wire 3 Frequency The frequency of alternating current will be either 50Hz or 60Hz depending upon the country. The frequency of direct current will be zero. 4 Direction It reverses its direction while flowing in a circuit. It only flows in one direction in the circuit. 5 Current It is the current of magnitude which is varying with time It is the current of constant magnitude. 6 Flow of Electrons Here electrons will keep switching the directions – forward and backward. Electrons move steadily in one direction or ‘forward’. 7 Obtained from The source of availability is A.C Generator and mains. The source of availability is either Cell or Battery. 8 Passive Parameters It is Impedance. Only Resistance 9 Power Factor It basically Lies between 0 & 1. It will be always 1. 10 Types It will of different types like Sinusoidal, Square Trapezoidal, and Triangular. It will be of Pure and pulsating.
  9. 9. SI Units Electrical Services
  10. 10. Conductor Electrical Services A substance which offers low resistance to the flow of electric current is called a conductor. Almost all pure metals are good conductors of electricity. Some important conductors in the order of their conducting ability are : silver, copper, aluminium, brass, zinc, nickel, iron, tin, lead, german silver, manganin, eureka, nichrome, tungsten and mercury. The following are the properties of a good conductor : (i) It should be of low cost. (ii) It should be easily available in the market. (iii) It should have sufficient tensile strength. (iv) Its joint should easily be made and soldered. (v) It should have sufficient mechanical strength. (vi) It should not be much effected by changing atmospheric conditions. (vii) It should have high conductivity and low specific resistance to keep the electrical losses as low as possible. (viii) It should have flexibility Properties of a good conductor
  11. 11. Conductor Electrical Services Classification of conductor (i) Bare conductor- Conductor which are not covered with insulation are known as bare conductors. They are used in overhead lines for transmission and distribution. (ii) Insulated conductors- Conductors which are covered with insulation are called insulated conductors. They are used for indoor wiring installations and underground distribution system. Semi-conductor Semi-conductors are special resistance alloys which offer fairly high resistance to the flow of current. Alloys and carbon have high resistance all they fall in this category. They are very valuable for making standard resistances. The important ones are Eureka or Constantan, German Silver, Manganin, Platinoid etc.
  12. 12. Difference between wire and cable Electrical Services Any conductor which is composed of a conducting material, and is uniform in diameter and circular in cross-section is called a wire. A length of a single insulated conductor (solid or stranded) or two or more such conductors, each provided with its own insulation which are laid up together is called a cable. The insulated conductor or conductors may or may not be provided with an overall mechanical protective covering. In short, any conductor which is provided with insulation is called a cable.
  13. 13. Electrical Services Difference between wire and cable Parts of a Cable (i) Conductor : Any pure metal which offers low resistance to the passage of electric current is called a conductor. The current is taken from one place to the other by means of a conductor. (ii) Insulation Covering : It is the covering which bounds the current to flow in a definite path. The insulation of the cable must be strong enough because a leakage current will start giving electrical shocks and can cause fire. The strength of insulation of the insulated cable depends upon dampness, heat and voltage. Damp and heat will reduce the insulation. (iii) Protective Covering : It protects the insulation covering against any mechanical injury. Stranded Cable Electrical energy is supplied from the generating station to the consumer by means of overhead lines or underground cables. The conductor of the cable is of two types : (i) Solid conductor (ii) Stranded conductor
  14. 14. Electrical Services Difference between wire and cable In a solid conductor cable, there is only one conductor. But in a stranded conductor cable, it is made of a number of strands of wires of circular cross-section so that it can become flexible. The number of strands used in a cable are 3,7, 19, 37, 61, 91, 127 or 169. These numbers are specifically chosen because they give a circular shape to the conductor of a cable. In a three-strand cable, two strands are twisted around the third strand. Similarly, in the case of seven or more strands the arrangements of the conductor is as given below: 7 Strands : Six strands are twisted around a central strand. 19 Strands : Seven strands are twisted as above and the rest of the 12 strands in a direction opposite to that of the previous layer. 37Strands:Nineteen strands as above and the remaining 18 strands for the additional layer in the opposite direction.
  15. 15. Electrical Services Types of Cables The following cables are used for different types of wiring installation. i. V.I.R (Vulcanized insulation rubber) cable ii. C.T.S (Cab tyre sheathed) cable iii. P.V.C (Poly vinyl chloride) cable iv. Lead-sheathed cable v. Weather-proof cable vi. Tropodure cable vii. Flexible cable Standard Wires The wires used for ordinary wiring purposes are of single solid conductors; but when the wires are required for greater flexibility, such as for a pendant lamp, wires of single conductors are not suitable. Difference between wire and cable
  16. 16. Electrical Services Difference between wire and cable Types of Wires Rubber covered, Taped, Braided, Compound Wires Double Braided Lead Alloy Sheathed Wires T.R.S or C.T.S wires Weather proof Wires
  17. 17. Electrical Services Difference between wire and cable Twin core flexible Wires Twin rubber insulated cord Twin twisted cotton braided flexible Wires Twin T.R.S flexible Wires
  18. 18. System of wiring Electrical Services Cleat wiring system- This is a very simple system and also the cheapest method of running wires and is used for temporary lighting at dry places. The wiring is run in the Visible condition except in places where they are likely to be protected from mechanical damage and less than 1.5 m above the ground level. Single core V.I.R. cables or P.V.C. insulated cables are used in this system. Cleat wiring Three-way cleat Two-way cleat
  19. 19. Electrical Services System of wiring These cables are run in the grooves of glazed porcelain cleats which are fastened in wooden wall plugs (“gutties”) by means of wood screws, the grooves of the porcelain cleat should neither compress the insulation nor be loose fitting. The cleat should be provided every 60 cm to avoid sag in the cables. Sharp bends should be avoided in the wiring and the spacing between the cleats should be reduced to prevent the touching of wall and sagging. Advantages- In this wiring faults can easily be located Disadvantages- It collects dust over the wire There is no protection from mechanical injury, fire, gas or water pipe.
  20. 20. Electrical Services System of wiring Wooden casing capping wiring system- it is suitable for low voltage domestic installation where vulcanised rubber- insulated cables or plasticinsulated cables are used. This wiring system is not used in damp places such as hilly areas as it absorbs moisture. The casing should be of well-seasoned teak wood, free from knots, damp and other defects. Before the installation of the casing capping, it should be well- varnished from all side with pure shellac varnish. Wooden casing capping wiring
  21. 21. Electrical Services System of wiring The casing is first installed by means of flathead, countersunk wood screws to the wooden plug (“gutties”) on dry walls or ceilings at an interval of not exceeding 90 cm for sizes upto 64 mm and not exceeding 60 cm for sizes above 64 mm casing. The casing should not be fixed near or under the gas, steam or water line. Advantages There is sufficient mechanical protection to the cable used Disadvantages There is a great risk of fire in this system It is difficult to find faults It is not damp proof . Although it is painted with shellace varnish, yet it absorbs moisture easily. Its erection is not very simple and therefore requires more time and skilled labour.
  22. 22. Electrical Services System of wiring Finished joints Two shaped casings to be joined together Finished corner joints
  23. 23. Electrical Services System of wiring C.T.S or T.R.S wiring system- In this wiring system, single, twin or three-core, tough rubber- sheathed cables are used for low-voltage wiring installation. It should be exposed to the sun and rain. However, PVC sheathed cables are also suitable for medium-voltage installation and they may be installed under exposed conditions of the sun, rain or damp places and where fumes of acid or alkalies are present. T.R.S. cables are fixed on well-seasoned, perfectly straight and well-varnished wooden battens by means of joint clips as explained in lead sheathed wiring system, not less than 10 mm in thickness (10 to 19 mm usually) and the width of which is such as to fit the total width of the cables laid on the batten (10 to 50 mm) . Wooden plugs used for fixing the batten should be fixed at a minimum interval of 60 cm (2’) apart or 75 cm (2 W) a part maximum. The wiring should not be given any right angle bend. C.T.S wiring
  24. 24. Electrical Services System of wiring The life of such a wiring system is about 30 years and is used in large buildings, hospitals and at places where chemical fumes and moisture are present. Advantages : The advantages of the system are as follows : (i) In this system, protection from dampness is excellent. (ii) This system requires semi-skilled labour for erection and therefore is less costly. (iii) Its life is very long. (iv) This system provides good mechanical protection to the cable used in the installation. (v) Its general appearance is very good.
  25. 25. Electrical Services System of wiring Conduit wiring system- This system of wiring can be divided into two further systems as follows : (i) Surface Conduit Wiring: This system is suitable for low and medium voltage wiring installations. V.I.R. or P.V.C. cables are run in metal pipes known as conduits which provide good mechanical protection to the insulation of the cable and reduce the risk of fire. The cables are drawn through the conduit pipe by means of a steel wire known as fish wire. Conduit pipes are available in various sizes which vary from 12 mm (1/2”) to 75 mm (3"). The size of the conduit to be selected for the wiring depends upon the diameter and the number of cables to be carried through the conduit.
  26. 26. Electrical Services System of wiring Surface conduit wiringIllustration of surface conduit wiring Concealed conduit wiring- In this system small channels are formed in the walls, ceiling etc When the building is under construction. The conduit pipes are erected in these channels by staples or saddles not more than 60 cm (2’) apart, inspection-type conduit accessories like inspection-tee, elbow or junction boxes are fitted flush mounted on the walls at a sufficient distance during the installation of the conduit to facilitate the drawing in or removal of wires. After the erection of the conduit pipes in the channels, these are closed and brought to the original finish of the wall. All the electrical accessories are fixed on an insulating sheet which is fitted on the cast iron boxes. This system of wiring has a neat and attractive appearance.
  27. 27. Electrical Services System of wiring Advantages • Mechanical protection for the insulation of the conductor is very good • It gives very good protection against fire due to short circuits etc. • It provides protection against moisture in the atmosphere as the conduit can be sealed properly. • Damaged cable can easily be replaced in this system. • It has a very neat and attractive appearance. Disadvantages • The initial cost of this system is very high • Danger of burrs due to bad workmanship causes the insulation of the cable to be damaged. • In damp conditions moisture condenses inside the conduit pipe and thus reduces the insulation resistance which may cause a short circuit between the cables.
  28. 28. Electrical Services System of wiring Rigid Conduit Joint between rigid conduit and flexible conduit Bottom half of the flexible coupling Top half of the flexible coupling Two screw flexible coupling
  29. 29. Ferrule type cartridge fuse with fuse link Fuses Electrical Services A fuse is a device for protecting a circuit against damage from an excessive current flowing in it, by opening the circuit on the heating of a fuse-element by the excessive current. A semi-enclosed fuse is one in which the fuse-element is neither in free air, nor totally enclosed, as it is in the cartidge fuse. The rewireable fuse may usually be classified as semi-enclosed. Types of fuse- Knife blade cartridge fuse with fuse link Screw plug type fuse Ordinary fuse Time delay fuse The renewal type cartridge
  30. 30. Electrical Services Fuses Fuse Holders- Totally enclosed fuse Semi enclosed fuse holder
  31. 31. References • K.B Bhatia, Electrical wiring estimating & costing • S.L. Uppal, Electrical wiring estimating & costing • K Domke, Light in the engineering, architecture and the environment • Joseph B. Wujek, Mechanical and electrical system in Architecture, Engineering and Construction • Rodiger Granslandt, Handbook of lighting design • Fred Hall, Building Services Handbook • David V Chadderton, Building Services Engineering Electrical Services
  32. 32. Thanks Electrical Services